(1) Field of the Invention
This invention relates to railway car center plate swivel connections and, more particularly, to railway car body center plate assemblies in which the bearing plate is an elastomeric pad having horizontal and vertical bearing surfaces.
(2) Description of the Invention
The swivel connection of railway vehicles comprises a center plate assembly disposed between the car body or frame and the truck, which allows the truck to turn under the car about a center pin. The center plate assembly conventionally used in railway cars comprises a body center plate attached to the underside of the body bolster and a truck center plate having the shape of a bowl and being secured to the top side of the truck bolster or cast integrally therewith. The body and truck center plates are provided with coaxial openings which receive a center pin therein to guide the engagement of the parts.
Under conditions in which railway cars are operated, breakage of the center plate assembly occurs much too frequently, especially in the larger cars currently coming into broad usage. During normal operation of railway freight cars, the body center plate is the structural member which, together with the side bearings, transfers the railway car load onto the truck. When in motion, the railway car rocks from side to side. When the car rocks to one side, the weight of the car is concentrated at a single line of contact near the peripheral edge of the horizontal bearing surface of the body center plate. This concentration of the car load at a single line of contact on the body center plate, plus the fact that it is intermittently applied and released, in many cases results in fatigue cracking of the center plate. Failure of the body center plate, or the means of its attachment, causes loss of car operating time while the center plate is being replaced or repaired.
Accordingly, there is a need for a railway car center plate assembly in which high-bearing stresses between the body center plate and truck center plate, induced by the car rocking back and forth on the edges of the body center plate as it bears on one side bearing and then the other, are eliminated, thus assuring a longer useful life for the body center plate. Further, there is a need for a center plate assembly that provides sufficient resistance to rotation of the truck to reduce the tendency of the truck to oscillate about the center plate, a condition known as "hunting".
An improved body center plate assembly design in which the horizontal bearing surface is an elastomeric pad is described in U.S Pat. No. 3,986,752. The body center plate assembly comprises.
(1) a base plate having a flat surface on its underside and a circular, central opening adapted for receiving a center pin;
(2) two concentric, cylindrical flanges extending downward from and perpendicular to the flat surface of the base plate encircling the central opening; and
(3) an annular, solid, synthetic elastomeric pad having horizontal bearing surfaces which is in contact with the flat surface on the underside of the base plate and is located within and substantially fills the annular space between the flanges of the body center plate. This body center plate represents a major advance, in that it distributes the load more evenly along the horizontal bearing surface. This assembly, however, does nothing to more evenly distribute the stress of horizontal forces between the body center plate annular flange and the sides of the truck center plate bowl encountered during braking and acceleration.